Preparation of cellulose ethers

ABSTRACT

An improved process is provided for preparing cellulose ethers of the viscosity desired. Their viscosity is regulated during or after the etherification reaction used in their preparation. The viscosity regulating agents used are an organic hydroperoxide in conjunction with a metal catalyst. Now preferred are tert butyl hydroperoxide in conjunction with a cobalt or manganese salt.

[ 1 March 6, 1973 PREPARATION OF CELLULOSE ETHERS [75] Inventor:

[73] Assignee: Hercules Incorporated, Wilmington,

' Del.

June 7, 1971 Eugene D. Klug, Wilmington, Del.

[22] Filed:

[21] App1.No.: 150,709

[52] US. Cl.....260/231 R, 260/231 A, 260/231 CM,

260/232 [51] Int. Cl. ..C08b 11/00 [58] Field of Search.......260/23l R,231 A, 231 CM, 232; 106/ 194 [56] References Cited UNITED STATES PATENTS2,517,835 8/1950 Branan et a1. 260/231 2,498,208 2/1950 Houk et a1..260/232 2,555,224 5/1951 Decker 106/194 2,912,431 11/1959 Leonard eta1. ..260/232 3,347,689 10/1967 Futami et a1. 106/194 FOREIGN PATENTS ORAPPLlCATlONS 587,328 4/1947 Great Britain .1260/232 PrimaryExaminer-Donald E. Czaja Assistant ExaminerRonald W. GriffinAttorney-William S. Alexander [57] ABSTRACT 9 Claims, No DrawingsPREPARATION OF CELLULOSE ETHERS This invention relates to a process ofpreparing cellulose ethers and more particularly to a process ofadjusting, controlling or regulating the viscosity of cellulose etherseither during or after the etherification reaction used in theirpreparation.

For many applications it is desirable to be able to prepare celluloseethers of low viscosity. Existing processes for accomplishing this arenot as satisfactory as desired. These prior art processes and theirdrawbacks will not be summarized.

1. Start with a special cellulose of the required degree ofpolymerization which will yield a product for each viscosity typedesired. This is very impractical because it requires keeping on hand alarge number of grades of cellulose.

2. Age alkali cellulose in the presence of air. One of the manydisadvantages of this process is the long time required, from severalhours for as long as two days.

3. Add a viscosity regulating agent either alone or plus certain metalcatalysts initially so that a large part of the degradation occurs inthe alkali/cellulose stage and the early part of the etherificationreaction. The viscosity regulating agents comprise hydrogen peroxide adalkali metal hypohalites, peroxides and periodates. The metal catalystscomprise a salt of a metal including manganese, cobalt, iron or othertransition metal. Although this is a good process and has beencommercially used, the extent to which the viscosity may be reduced andthe efficiency of the process are limited.

According to the present invention it has been found that the foregoingdisadvantages are overcome or at least minimized and the viscosity ofthe cellulose ethers are satisfactorily regulated during preparationthereof, by reaction of a mixture of alkali and cellulose with anetherifying agent, by carrying out the process which comprises adding tothe reaction mixture of an alkali and cellulose with an etherifyingagent an organic hydroperoxide and a salt of a metal of manganese,cobalt, iron, or other transition metal, and conducting said reaction inthe presence thereof. Although regulating the viscosity of the celluloseethers during the etherification reaction is preferred since it is moreefficient, the invention is also applicable to regulating the viscosityof the cellulose ethers after etherification has been completed.

Reducing the viscosity after the etherification proper has beencompleted may be accomplished by treatment of either the crudeetherification reaction mixture or the purified product in a suitablediluent. In some cases, e.g., in the preparation ofcarboxymethylcellulose (CMC), it is possible to conduct the viscosityreduction on the crude CMC. However in other cases, e.g., in thepreparation of water soluble hydroxyethylcellulose (l-lEC), it ispreferred to reduce the viscosity after purification because the lowermolecular weight product is very soluble in the purification solventsand therefore difficult to isolate from them. In any case the organichydroperoxide and metal catalyst are added to an aqueous or organicsolvent slurry of the cellulose ether and the slurry is heated for about0.5-6 hours at a temperature of about 70C. 140C. The viscosity reducingagent can be added at any time during or after the process of preparingthe cellulose ether as long as there is sufficient time to accomplishthe amount of viscosity reduction desired. In during preparation ofviscosity reduction, preferably it is added at the start (i.e., alkalicellulose stage). In after preparation of viscosity reduction,preferably it is added to the purified ether.

The terms "degree of substitution (D.S. and M.S.) used herein are wellunderstood. There are three hydroxyl groups in each anhydroglucose unitin the cellulose molecule. D.S. is the average number of hydroxyl groupssubstituted in the cellulose per anhydroglucose unit. M.S. is theaverage number of molecules of reactant combined with the cellulose peranhydroglucose unit.

The following examples illustrate specific embodiments of the presentinvention. These examples are not intended to limit the presentinvention beyond the scope of the claims. In the examples and elswhereherein parts, percent and ratios are by weight, and the amount of alkaliis the total amount based on sodium hydroxide, unless otherwisespecified. All viscosities were determined with a standard BrookfieldLVF Synchrolectric viscometer at 25G., and in water unless otherwisespecified. Where viscosity is given as greater than 100,000 cps it meansthat it was beyond the capacity of the viscometer and therefore too highto measure, and usually the dispersion of the material formed a solidmass.

EXAMPLE 1 HPC Example 1 shows using this invention to regulate theviscosity of hydroxypropyl cellulose (HPC) during its preparation.

A pressure reactor equipped with agitator was charged as follows:

Ingredient Parts Cellulose 1.0 Total NaOH 0.31 Heptane l7 Tert butanol3.0 Water 0.45 TBHP" 0.24 Cobalt (added as CoCl,) 50 X 10" (a) tertbutyl hydroperoxide (b) 50 ppm based on the cellulose The reactionmixture was stirred for one hour at room temperature after which 3.4parts of propylene oxide was added. The air in the reactor was displacedwith nitrogen and the reaction mixture was heated to C. in 1 hour andkept at 70C. for 16 hours. The heptane liquor was filtered off. Thefilter cake was slowly added to hot (C. C.) water with stirring, theheptane flashing off, and the alkali was neutralized with acetic acid.The HPC product was then washed thoroughly with hot water and dried. Thedried HPC had excellent solubility in water and in alcohol. It had anM.S. of 3.7. A 10 percent aqueous solution had a viscosity of 70 cps.The viscosity of a 10 percent HPC aqueous solution prepared under thesame conditions without regulation was greater than 100,000 cps.

EXAMPLES 2 6 HPC The effectiveness of this invention and the influenceof catalyst in regulating the viscosity of HPC during its preparationare illustrated in Table I below. The same process conditions givenabove for Example 1 were used except as otherwise shown. The MS. of theproducts was about 4.

TABLE I Viscosity, cps.

Ex. Variable (10% solution) 2 TBHP Cobalt 70 3 No organic hydroperoxidenor metl 100,000 catalyst 4 TBHP but no catalyst 2,935 5 TBHP &Manganese 105 6 TBHP & lron 550 (a) Added as manganous sulfate (b) Addedas ferrous chloride in combination with citric acid as a chelatingagent.

EXAMPLES 7- HPC The effect of alkali/cellulose ratio on viscosityregulation during preparation of HPC, HPC quality and MS. is given inTable II below. Except as otherwise shown (primarily said ratios andrecipe given below) the process conditions of Example 1 were used. Thefollowing recipe was used.

Ingredient Parts Cellulose 1.0

Heptane l7 Tert butanol 1.4

Water 0.45

TBHP 0.08

Cobalt (added as C00,) 50 X 10' Propylene oxide 3.0 (a) 50 ppm based onthe cellulose Table II Total NaOH/ Viscosity, cps Water HydroxypropylEx. Cell. 10% Solution Solubility MS 7 0.1 270 good 3.3 8 0.135 170 good3.5 9 0.185 100 good 4.1 10 0.235 85 good 4.05

(a) without viscosity regulation 10% solution viscosities of HPCproducts were l00,000 cps.

Organic hydroperoxides have acidic characteristics and during the courseof their decomposition consume a certain amount of NaOI-I. It istherefore desirable to add additional NaOh up to approximately one moleper mole of organic hydroperoxide being used over and above the normalamount of NaOH used where viscosity reduction is not being carried out.

As is well known, the alkali/cellulose ratio employed during preparationof cellulose ethers varies greatly depending upon the derivative beingprepared. For example, in the preparation of hydroxypropyl cellulosewith an MS. above 2.0 the preferred ratio of NaOI-I/cellulose is in therange of about 0.05/1 0.2/1. Thus, when an organic hydroperoxide isadded at a ratio of 0.25 parts per part of cellulose to reduce theviscosity during etherification approximately a molar equivalent amountof excess alkali is added to neutralize the hydroperoxide decompositionproducts and the preferred ratio of NaOH/cellulose is increased to therange of about 0.15/1 0.30/1. For preparing HEC without viscosityreduction the preferred alkali/cellulose ratio is in the range of about0.35/1 0.4/1, and when an organic hydroperoxide at the above mentionedratio is added to reduce the viscosity during etherification thepreferred range of NaOH/cellulose is increased slightly to about 04/10.5/1. On the other hand, for preparation of carboxymethylcellulose of aD.S. of 0.8 the preferred range of NaOH/cellulose without viscosityreduction is in the range of about 0.5/1 06/1, and when an organichydroperoxide at the above mentioned ratio is added to reduce theviscosity during etherification the preferred range of NaOH/cellulose isincreased slightly to about 0.55/1 0.65/1. For ethyl cellulosepreparation in which a large excess of alkali is used (about 5/1 7/1ratio of NaOH to cellulose) little or no adjustment is needed tocompensate for the hydroperoxide.

When the viscosity reduction is carried out using an organichydroperoxide following etherification, no alkali need be added but thepresence of a small amount will increase the efficiency of the viscosityreduction process. Thus, depending upon the amount of organichydroperoxide used in the viscosity reduction operation, alkali(expressed as NaOH) in the weight ratio of cellulose of up to about 0.2and usually about 0.05 0.2 may be added.

If an alkali other than NaOl-l, e.g., KOH or LiOl-I, is employed it willbe understood that the weight ratio in relation to the cellulose shouldbe adjusted to provide substantially the same molar amount of alkali.

EXAMPLES ll 14 HPC A comparison of TBHP of this invention with prior artH 0 viscosity regulating agent during preparation of HPC is given inTable III below. Except as otherwise shown the same process conditionsof Example 1 were used.

In Examples 11-14 the weight ratios to cellulose were heptane 17, tertbutanol 1.4, and propylene oxide 3.0. In Examples 13 and 14 the higher HO input shown resulted from the water present in the 30 percent H Oused. In these two pairs of substantially identical examples at twodifferent levels of viscosity regulating agent, prior art H O gaveproducts having 24 and 53 times the viscosities of products preparedwith TBHP according to this invention.

Table III Parts per part Cellulose Viscosity, Hydorxy- Total cps propylEx. CO" H O, TBHP NaOI-I H O Solution MS 11 soxltr 0.08 0.22 0.45 55603.6 12 50X10 0.08 0.22 0.45 230 3.5 13 50Xl0 0.24 0.255 0.59 3170 3.1 1450X10' 0.24 0.255 0.59 3.1

(a) 50 ppm based on the cellulose and added as CoCl (b) withoutviscosity regulation 10% solution viscosities of HPC products were100,000 cps.

EXAMPLES 15-18 HPC Using substantially the same process conditions ofExample 1 except where otherwise indicated, Examples 15-18 compare TBHPwith other organic hydroperoxides in the preparation of HPC. Propyleneoxide/cellulose ratio was 3.0 and the amount of cobalt was 50 ppm basedon the cellulose (added as CoCl The HPC products had an M.S. of about3.5. Further details are given in Table IV below.

TA B L E lV 'Hydroperoxides Ratio to Viscosity, cps.

Ex. Name cellulose solution p-menthane hydroperoxide 0.153 190 16diisopropylbenzene hydroperoxide 0. 173 905 17 cumene hydroperoxide0.128 660 I 18 tert butyl hydroperoxide (TBHP) 0.080 80 (a) added as 50%concentrate in p-methane (b) added as 50% concentrate indiisopropylbenzene (c) added as 75% concentrate in cumene anddimethylbenzyl alcohol These ratios of organic hydroperoxides tocellulose in Table IV above represent 0.00089 gram mole of hydroperoxideper gram of cellulose or about 0.145 mole hydroperoxide peranhydroglucose unit of the cellulose. Although TBHP was the mostefficient, the other organic hydroperoxides tested were quitesatisfactory and far more efficient than the leading prior art hydrogenperoxide viscosity regulator. This is evident from Examples 15-18 whichshow that viscosities of 190-905 cps. were obtained at organichydroperoxide ratios of 0.128-0173, whereas by contrast hydrogenperoxide at the much higher ratio to cellulose of 0.24 (0.007 gram moleper gram cellulose) gave a viscosity of 3170 cps. (Example 13). Withoutviscosity regulating agent the viscosity was greater than 100,000 cps.

EXAMPLES 19 21 Modified HPC Use of this invention in regulating theviscosity of HPC ethers modified with other etherification agents duringtheir preparation is shown in Table V below. The process conditions usedin making these ethers were substantially identical with those used inmaking the unmodified HPC ethers of Example 1 with the followingexceptions. The modifier reagent was added along with the propyleneoxide. In the benzyl modification an additional amount of NaOH was addedequal to one mole of NaOH per mole of benzyl chloride.

TABLE V Modifier Modifier( )Viscosity.(bl Modifier Reagent Substicps 10%Ex. Modification Reagent Cell tution Solution 19 Benzyl Benzyl 0.2 0.1 11 10 Chloride 20 Aminoethyl Ethylene- 0.125 0.18 37 imine 21 Phenyl Hy-Styrene 0.525 0.12 345 droxyethyl oxide (a) In each Example thehydroxypropyl substitution (M.S.) was ap proximately 4. (b) Theviscosities of 10% aqueous solutions of these modified HPC ethers beforeviscosity reduction were greater than 100,000 cps.

The comparison between the efficiency of TBHP of this invention and theleading prior art H 0 as viscosity regulating agents in Examples 19-21was substantially the same as is shown for Examples 1 1 l4.

EXAMPLES 22-24 HEC TABLE VI Viscosity.cps. Total NaOl-l/ Cobalt] TBHP/10%S0lution Ex. Cellulose cellulose" cellulose in 5% NaOH 22 0.34 ZeroZero 17,540 23 0.37 50 .08 80 24 0.44 50 .16 27 (a) ppm cobalt based oncellulose (added as CoCl,) (b) 8% solution, a 10% solution was greaterthan 100,000 cps.

EXAMPLES 25 28 CARBOXYMETHYLCELLULOSE (CMC) Use of this invention inregulating the viscosity of CMC during its preparation is shown in TableVII below.

A slurry of 1 part wood pulp, 9.8 parts isopropanol, 1.53 parts water,50 ppm cobalt based on the cellulose (added as CoCl and the indicatedamounts of TBHP and NaOH were stirred for 45 minutes at roomtemperature. Then 0.64 part monochloroacetic acid was added and theslurry was stirred at room temperature for 15 minutes. The air wasdisplaced with nitrogen and with continued stirring the reaction mixturewas heated to C. in one hour and kept at that temperature for threehours. The products were worked up by neutralizing the alkali withacetic acid, washing with percent methanol, dehydrating with anhydrousmethanol and drying at 70C. in vacuo.

TABLE VII carboxytt Total Viscosity, cps.methyl Ex. NaOH/cell TBHP/cell.10% SolutionD.S.

25 0.575 0.04 14550.75 26 0.605 0.12 1600.78 27 0.65 0.24 700.81 28 0.55Zero 100,0000.76

EXAMPLES 29 34 ETHYL'CELLULQSE 130C.140C. for 2% hours. The pressure wasthen released, venting of byproducts diethyl ether and ethanol to therecovery system. The ethyl cellulose product was water washed free ofsalts and alcohols and dried. it has an ethoxyl D8 of about 2.5; percentsolutions were prepared in a 4 to 1 by weight toluenealcohol mixture andtheir viscosities measured. Table VIII below gives further details.

TABLE vnr Viscosity, cps.

ex.- TBHP/cellulose total NaOH/cellulose 5% Soultions 29 Zero 6.8 2000(gel) 30 0.013 6.8 2000 (gel) 31 0.025 6.8 45 32 0.050 6.8 10.6 33 0.106.8 5.0 34 0.20 6.8 Too low to measure EXAMPLES 35-38 HPC TABLE 1XExample 35 36 37 38 TBHP/HPC 0.10 0.10 0.10 0.10 Total NaOH/HPC zero0.02 0.04 0.06 Viscosity after treatment (2%) 120 30 24 23 EXAMPLES39-45 Examples 39-45 show using this invention to regulate the viscosityof water soluble HEC after the etherification reaction.

One part water soluble HEC OF M.S. 2.5 and viscosities in 2 percent and5 percent aqueous solution of 6000 and greater than 100,000 cpsrespectively was charged into a stirred reactor with 3.2 parts of 96percent acetone, 50 ppm cobalt based on HEC (added as CoCl and theindicated amount of TBHP. The air in the vessel was displaced withnitrogen and the reaction mixture was heated for 0.5 hour at 120C. andthen dried. Table X below gives further details.

TABLE X 45 zero 6000 100,000

EXAMPLE 46 CMC This example shows use of this invention in regulat- 7ing the viscosityof CMC by adding a viscosity regulating agent (TBHP) atthe end of the etherification reaction but before the CMC has beenpurified and recovered.

A slurry of 1.0 part cellulose, 0.58 part NaOH and 11.2 parts of 87percent isopropanol was stirred for 45 minutes at 25C-30C. Then 0.64part monochloroacetic acid dissolved in 0.64 part of 87 percentisopropanol was added and the reaction mixture was heated to C. in 30minutes, and maintained at 70C. for 90 minutes. To the resulting crudeCMC was added 0.5 part TBHP and 50 ppm cobalt based on the cellulose(added as CoCl Then the mixture was heated an additional 30 minutes at70C The resulting viscosity regulated CMC product was neutralized withacetic acid, purified by washing with percent methanol and dried. TheCMC product had a D.S. of 0.78. A 2 percent aqueous solution has aviscosity of 69 cps and a 10 percent aqueous solution had a viscosity of1 1,000 cps. In contrast to this, 2 percent aqueous and 5 percentaqueous solutions of an identical CMC product prepared by the sameprocess, except not subjected to the treatment with TBI-IP and cobalt,had viscosities of 800 cps and greater than 100,000 cps respectively.

Viscosity regulating agents applicable herein include organichydroperoxides together with certain metal catalysts. The organichydroperoxides include, e. g., tert butyl hydroperoxide (TBHP), cumenehydroperoxide, p-menthane hydroperoxide, diisopropylbenzenehydroperoxide. The organic hydroperoxide viscosity regulating agents arenormally available and are used as concentrated solutions in organicsolvents. For example, TBI-IP may be obtained as a 70-90 percentsolution in water percent solutions used in the examples). Cumenehydroperoxide is available as a 79-85 percent solution in cumene anddimethylbenzyl alcohol (75 percent solutions used in the examples).Diisopropylbenzene hydroperoxide and p-menthane hydroperoxide areavailable as approximately 50 percent concentrates in the correspondinghydrocarbons. In all the examples the quantities employed are expressedon a basis.

The preferred metal catalysts comprise salts of manganese and cobalt,although salts of iron, lead, vanadium, copper and other transitionmetals may be employed. Salts of the metals which may be employedinclude, e.g., the chloride, nitrate, acetate, bromide, sulfate,naphthenate. The metal salts may also be used in chelated form. Variouschelating agents are effective, e.g., ethylenediamine tetraacetic acid,gluconic acid, citric acid, pyrophosphoric acid.

Tert butyl hydroperoxide used in conjunction with a manganese or cobaltsalt is a preferred viscosity reducing agent.

The amount of organic hydroperoxide can vary over a wide range. Itdepends on a number of factors including the extent of degradationdesired, the molecular weight of the starting cellulose, and theparticular organic hydroperoxide used. Generally, an organichydroperoxide/cellulose or cellulose ether weight ratio of about0.002-0.5, preferably about 0.025-0.25, gives products of the desiredviscosity for most uses.

The amount of metal catalyst (calculated as the metal and based on thecellulose) can vary over a wide range. The amount depends on a number offactors including those in the immediately preceding paragraph plus thepartciular catalyst used. Generally about 10-100 ppm based on thecellulose or cellulose ether, preferably about -50 ppm, metal catalystgives products of the desired viscosity for most uses.

This invention is applicable to the preparation of cellulose ethers,including water soluble, alkali soluble and/or organo soluble, preparedby prior art slurry (i.e., in presence of inert organic diluent) ornonslurry (i.e., in absence of inert organic diluent) processes,although it is particularly applicable in making water soluble celluloseethers by conventional slurry processes. Typical celulose ethersinclude, e.g., hydroxyethyl cellulose ethers (e.g., hydroxyethylcellulose, hydroxypropyl cellulose), carboxyalkyl cellulose hydroxyethyl(e.g., carboxymethylcellulose), alkyl cellulose ethers (e.g., methylcellulose, ethyl cellulose), mixed cellulose ethers for instancecarboxyalkyl hydroxyalkyl cellulose ethers (e.g., carboxymethylhydroxyethyl cellulose, carboxymethyl hydroxypropyl cellulose), alkylhydroxyalky cellulose ethers (e.g., ethyl hydroxyethyl cellulose, methylhydroxypropyl cellulose), those in parenthesis being the most typicalindividual compounds.

The time-temperature conditions for carrying out the etherificationreactions on cellulose need not be modified from those conventionallyused to utilize the improvement of this invention whereby the molecularweight of the cellulose is decreased during its conversion to an etherderivative. When the organic hydroperoxide is added initially to thecellulose-alkalietherification agent mixture the viscosity reductionprobably occurs rapidly under the etherification conditions, beingessentially completed during the early stages of the reaction.Alternatively the hydroperoxide can be added at any time during theetherification reaction as long as a reaction time'of at least about hhr. at a temperature of at least about 70C. is provided to effect theviscosity reduction reaction.

If the viscosity reduction is carried out on the cellulose etherderivative subsequent to the completion of the etherification reaction,a reaction period in the range of about A to 6 hrs. at a temperature ofabout 70C.-140C. is used depending on the derivative and amount ofhydroperoxide used as well as the degree of viscosity reduction desired.

What l claim and desire to protect by Letters Patent 1. In thepreparation of a cellulose ether by reaction of a mixture of alkali andcellulose with an ether-ifying agent, the improvement which comprisesregulating the viscosity of the cellulose ether by adding to thereaction mixture,per part of cellulose, 0.002 to 0.5 part of an organichydroperoxide and 10 to parts of a transition metal, per million partsof cellulose, and conducting said reaction in the presence thereof, saidmetal being added in the form of a salt.

2. Process of reducing the viscosity of a cellu-lose ether which comrises heatin same in the presence of per part of cellu ose, 0.002 0 0.5part of an organic hydro-peroxide and 10 to 100 parts of a transitionmetal per million parts of cellulose ether, said metal being added inthe form of a salt.

3. In the preparation of a cellulose ether by reaction of a mixture ofalkali and cellulose with an etherifying agent, the improvement whichcomprises regulating the viscosity of the cellulose ether by adding tothe reaction mixture, per part of cellulose, 0.002 to 0.5 part of anorganic hydroperoxide and 10 to 100 parts of manganese or cobalt permillion parts of cellulose and conducting said reaction in the presencethereof, said manganese or cobalt being added in the form of a salt.

4. Process of claim 1 wherein the organic hydroperoxide is tert butylhydroperoxide.

5. Process of claim 1 wherein the cellulose ether is hydroxypropylcellulose, carboxymethylcellulose or ethyl cellulose and the organichydroperoxide is tert butyl hydroperoxide.

6. Process of reducing the viscosity of a cellulose ether whichcomprises heating same in the pre-sence of, per part of cellulose ether,0.002 to 0.5 part of an organic hydroperoxide, and 10 to 100 parts ofmanganese or cobalt per million parts of cellulose ether, said manganeseor cobalt being added in the form of a salt.

7. Process of claim 6 wherein hydroperoxide is tert butyl hydroperoxide.

8. Process of claim 6 wherein the cellulose ether is hydroxypropylcellulose, carboxymethylcellulose ether cellulose and the organichydroperoxide is tert butyl hydroperoxide.

9. Process of claim 6 wherein the cellulose ether is hydroxyethylcellulose and the organic hydroperoxide is tert butyl hydroperoxide.

the organic Column 1, line 27; "ad" should read -and a Column 2; line27; "25G. should read -25C.

Column 3 Table 1 "TBHP Cobalt 'shou ld read -TBHP & Cobalt- Column 3,line 3 under Table I; fil" should read -metal- Column 6, Table VII;

TABLE vn carboxy- 1: Total Viscosity, c smem l Ex. NaOH/ccfl TBHP/ccll.10% SolutionDS.

25 I 0.575 0.04 [455075 26 0.605 0.12 1600.78 27 0.65 0.24 700.81 280.55 Zero 100.0000 76 should read Table v I I Total Viscosity, cps.Carboxymeth Ex. NaOH/Cell. TBHP/Cell. 10% Solution D .S.

28 0.55 Zero l00,000 0.76

UNETED STATES FATENT OFFECE CERTEFEQATE F QQREQ'NQN Patent NO- 3 .119.663 Dated March -6 1973 Inventofls) Euq eheD. Kluq (Case 215 I It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

POWSO UNHED STATES PATENT @FFECE fiERTEFiQA'iE QQRREQ'HON Patent No.3,719,663 Dated March 6, 1973 Inventofls') Eugene D. Klug (Case 21) QPage 2 It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

- Column 7, line 33; "(85C.-TC) should read -s5c.-9o c)-- Column 9, line8; "particiular should read --particular- Column 9, line 19, "shoularead -c-ellulose---- Column 9, lines 19 & 20,; "hydroxyethyl" shouldread -hydroxyalkyl Column 9, line 22; *hydroxyethyl" should read-ethers-' Column 9, line 27; "hydroxyalky" should read --hydr0xyalkyl.

Column 1G, Claim 8, line 45; "ether" should read ---or ethyl---- Column10, Claim 1, line 2; Claim 2, lines 1 & 4;

Claim 6, line 2; several words have been hyphenated in the middle ofsentences which is incorrect.

Signed and sealed this 25th day of December 1973.

(SEAL) Attest:

EDWARD M. FLETGHER,JR. RENE D. TEGI'MEYER Attesting Officer ActingCommissioner of Patents

1. In the preparation of a cellulose ether by reaction of a mixture ofalkali and cellulose with an ether-ifying agent, the improvement whichcomprises regulating the viscosity of the cellulose ether by adding tothe reaction mixture,per part of cellulose, 0.002 to 0.5 part of anor-ganic hydroperoxide and 10 to 100 parts of a transition metal, permillion parts of cellulose, and conducting said reaction in the presencethereof, said metal being added in the form of a salt.
 2. Process ofreducing the viscosity of a cellu-lose ether which comprises heatingsame in the presence of per part of cellulose, 0.002 to 0.5 part of anorganic hydro-peroxide and 10 to 100 parts of a transition metal permillion parts of cellulose ether, said metal being added in the form ofa salt.
 3. In the preparation of a cellulose ether by reaction of amixture of alkali and cellulose with an etherifying agent, theimprovement which comprises regulating the viscosity of the celluloseether by adding to the reaction mixture, per part of cellulose, 0.002 to0.5 part of an organic hydroperoxide and 10 to 100 parts of manganese orcobalt per million parts of cellulose and conducting said reaction inthe presence thereof, said manganese or cobalt being added in the formof a salt.
 4. Process of claim 1 wherein the organic hydroperoxide istert butyl hydroperoxide.
 5. Process of claim 1 wherein the celluloseether is hydroxypropyl cellulose, carboxymethylcellulose or ethylcellulose and the organic hydroperoxide is tert butyl hydroperoxide. 6.Process of reducing the viscosity of a cellulose ether which comprisesheating same in the pre-sence of, per part of cellulose ether, 0.002 to0.5 part of an organic hydroperoxide, and 10 to 100 parts of manganeseor cobalt per million parts of cellulose ether, said manganese or cobaltbeing added in the form of a salt.
 7. Process of claim 6 wherein theorganic hydroperoxide is tert butyl hydroperoxide.
 8. Process of claim 6wherein the cellulose ether is hydroxypropyl cellulose,carboxymethylcellulose ether cellulose and the organic hydroperoxide istert butyl hydroperoxide.